Reader for wireless identification ic tag and wireless identification ic tag system

ABSTRACT

A reflected electromagnetic wave received, for example, from a wireless identification IC tag through an antenna ( 105 ) is processed not by a complicated circuit, but by capacitors ( 107, 100 ) and diodes ( 108, 109 ). By the combination of the capacitors ( 107, 100 ) and the diodes ( 108, 109 ), a voltage of the reflected electromagnetic wave is integrated. The reflected electromagnetic wave becomes different in voltage depending on a signal “0” and a signal “1” from the wireless identification IC tag. As a result, since an integrated value outputted to a reception signal line ( 113 ) becomes also different, it is possible to discriminate the signal “0” and the signal “1” in the reader for wireless identification IC tag. Since integration is utilized, even a week signal can be discriminated.

TECHNICAL FIELD

The present invention relates to a reader for a wireless identificationIC tag and a wireless identification IC tag system wirelessly performingidentification, and belongs to a technical field forming an economicalcircuit.

BACKGROUND ART

A wireless identification IC tag has an excellent function than aconventional bar-code because of its reading performance, security,compactness, and the like. This wireless identification IC tag isconsidered to come into wide use according to an improvement of itseconomical efficiency. In this case, a reader for the wirelessidentification IC tag is mounted even in a mobile terminal, andtherefore, a necessity for simply reading the wireless identification ICtag at any place arises. Consequently, a simple circuit for economicallyfabricating the reader for the wireless identification IC tag isrequired.

Patent Document 1 (Japanese Patent Application Laid-Open Publication No.2005-101892) discloses a method for simply performing control of awireless identification IC tag and a reader for the wirelessidentification IC tag with a reflected modulated signal by a delayelement in communications performed by using a backscatter system.

Patent Document 2 (Japanese Patent Application Laid-Open Publication No.2000-49654) discloses a method for simply performing control of awireless identification IC tag and a reader for the wirelessidentification IC tag by setting the antenna output electric power fromthe reader to two kinds of antenna output electric powers having adouble intensity difference at predetermined constant intervals of time.

Patent Document 1: Japanese Patent Application Laid-Open Publication No.2005-101892 Patent Document 2: Japanese Patent Application Laid-OpenPublication No. 2000-49654 DISCLOSURE OF THE INVENTION Problems to beSolved by the Invention

The present invention provides a simple circuit to mount a reader for awireless identification IC tag in a mobile terminal. An UHF bandwidthand a 2.45 GHz bandwidth are effective frequencies for an expansion ofthe communication distance for the wireless identification IC tag.However, since they are high in frequencies as compared with a 13.56 MHzbandwidth and a 125 kHz bandwidth, a receiver circuit has beencomplicated. Hence, it has been difficult to simplify the circuit, anddue to the circuit scale and the consumption electric power being large,accommodation into the mobile terminal has been difficult. If it is asimplified circuit, it will be advantageous even in case it is made intoan integral circuit of one chip, but in the conventional documents, nodisclosure of such an introduction of efficiency has been made.

Means for Solving the Problems

The typical ones of the inventions disclosed in this application will bebriefly described as follows.

A reader for a wireless identification IC tag according to the presentinvention processes a reflected electromagnetic wave from the wirelessidentification IC tag not by a complicated circuit, but by a capacitorand a diode. A voltage of the reflected electromagnetic wave isintegrated by a combination of the capacitor and the diode. Thereflected electromagnetic wave becomes different in voltage depending ona signal “0” and a signal “1” from the wireless identification IC tag.As a result, the integrated value becomes also different, and it istherefore possible to identify the signal “0” and the signal “1” in thereader for the wireless identification IC tag. By having a constructionto identify the reflected electromagnetic wave by the integral circuitin this manner, the reader for the wireless identification IC tag can berealized in a small circuit scale. Further, since an integral isutilized, even a week signal can be identified.

EFFECTS OF THE INVENTION

To briefly describe effects obtained by a typical aspect of theinvention disclosed in the present application, a reader for a wirelessidentification IC tag and a wireless identification IC tag system havinga small number of elements and excellent in economic efficiency can berealized.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a diagram illustrating a circuit of a reader for wirelessidentification IC tag of the present invention;

FIGS. 2A-2D are diagrams illustrating waveforms of the reader forwireless identification IC tag of the present invention;

FIGS. 3A-3D are other diagrams illustrating waveforms of the reader forwireless identification IC tag of the present invention;

FIG. 4 is another diagram illustrating a circuit of a reader forwireless identification IC tag of the present invention;

FIG. 5 is another diagram illustrating a circuit of a reader forwireless identification IC tag of the present invention;

FIG. 6 is a diagram illustrating a configuration example of a wirelessidentification IC tag system of the present invention; and

FIG. 7 is a diagram illustrating a circuit of a reader for wirelessidentification IC tag studied as a premise of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. Note that componentshaving the same function are denoted by the same reference symbolsthroughout the drawings for describing the embodiment, and therepetitive description thereof will be omitted.

First Embodiment

To describe the embodiments of the present invention, a positioning of awireless identification IC tag and a reader for wireless identificationIC tag in the present invention will be described. FIG. 6 is a diagramillustrating a configuration example of the wireless identification ICtag system of the present invention. The wireless identification IC tagsystem of the present invention is configured by the reader for wirelessidentification IC tag including a transmitting and receiving circuit602, an antenna 105 and a control circuit (first circuit) 601, and thewireless identification IC tag including a wireless identification ICtag chip 606 and a wireless identification IC tag antenna 605, and soforth. The control circuit 601 can be also provided outside of thereader for the wireless identification IC tag depending oncircumstances.

At the time of performing wireless communications, first, a controlsignal 112 is transmitted to the transmitting and receiving circuit 602from the control circuit 601. Upon receipt of the control signal line112, the antenna 105 connected to the transmitting and receiving circuit602 transmits a transmission electromagnetic wave 603. The wirelessidentification IC tag chip 606 is mounted with the wirelessidentification IC tag antenna 605, and receives the energy and signal ofthe transmission electromagnetic wave 603. This energy enables aninternal voltage of the wireless identification IC tag chip 606 toincrease by a rectification circuit provided inside the wirelessidentification IC tag chip 606, thereby putting the chip into anoperable state. Further, the wireless identification IC tag chip 606 isoperated according to a modulating signal from the transmissionelectromagnetic wave 603, thereby operating an internal memory circuit.Information in a memory is transmitted to the antenna 105 one bit by onebit by the reflected electromagnetic wave 604. The received signal isdemodulated by the transmitting and receiving circuit 602, and istransmitted to the control circuit 601 by a reception signal line 113. Areceived signal is processed inside the control circuit 601, and iseffectively utilized as being connected to a network or a personalcomputer, a mobile terminal, and the like and delivered to a softwarefor application.

FIG. 1 is a diagram illustrating a circuit of the reader for wirelessidentification IC tag of the present invention. A high-frequencygenerator 101 is connected to a NOR circuit 102. A control signal line112 is also connected to this NOR circuit. An output from the NORcircuit 102 is inputted to a circulator 104 as a transmission line 103.The circulator 104 is connected with the antenna 105, and a reflectedwave reception signal from the antenna 105 is outputted to a receptionline 106.

The reception signal of the reception line 106 is inputted to a firstcapacitor 107. This first capacitor 107 plays a role of fixing anamplitude voltage of the reception signal. An output of this firstcapacitor 107 is inputted to a first diode 108 and a second diode 109.This first diode 108 plays a role of fixing the lowest level of thereception signal. The second diode 109 has a role of transmitting theenergy to one direction. An output of the second diode 109 is connectedto a second capacitor 110. The second capacitor 110 has a role ofaccumulating the energy from the second diode 109. A function ofdischarging the energy of the second capacitor at right timing isrealized by a MOS transistor 111 to serve as a switch. The MOStransistor 111 is controlled by the control signal line 112. An outputof the second capacitor 110 is outputted as the reception signal line113. In this manner, the circuit of the present invention requires onlyone system, and it is unnecessary to prepare a circuit of two systemssuch as a first detector circuit and a second detector circuit as shownin FIG. 7.

FIG. 7 is a diagram illustrating a circuit of a reader for wirelessidentification IC tag which performs detection by frequency. Ahigh-frequency generator 101 is connected to a NOR circuit 102. Acontrol signal line 112 is also connected to this NOR circuit. An outputfrom the NOR circuit 102 is inputted to a circulator 104 as atransmission line 103. The circulator 104 is connected with an antenna105, and a reflected wave reception signal from the antenna 105 isoutputted to a reception line 106. High frequency signals of thereception line 106 and the transmission line 103 are divided into twosignals by a first two-way distributor 701 and a second two-waydistributor 702, respectively. One of two output signals of the firsttwo-way distributor 701 is phase-shifted by a 90-degree phase shiftcircuit 709. The first detection circuit 703 detects a signal by usingone line of the signal distributed into two signals by the first two-waydistributor 701 and the second two-way distributor 702. Specifically, ahigh-speed mixer circuit and the like are employed. An output of thissignal is amplified by a first amplifier circuit 704, and further, it isregenerated by a first data regeneration circuit 705 using a band-passfilter and the like, and is inputted to an OR circuit 710.

A second detection circuit 706 detects a signal by using one line of thesignal distributed into two signals by the first two-way distributor 701and the second two-way distributor 702. A point different from the firstdetection circuit 703 is that a signal phase-shifted by the 90-degreephase shift circuit 709 is entered. For this circuit, specifically, ahigh-speed mixer circuit and the like are employed. An output of thissignal is amplified by a second amplifier circuit 707, and further, itis regenerated by a second data regeneration circuit 708 using aband-pass filter and the like, and is inputted to the OR circuit 710. Anoutput of the OR circuit 710 is outputted to a reception signal line113. In this manner, since the detection is made by high frequencies ofthe transmission signal, for example, by the frequencies such as 950 MHzof the UHF bandwidth and 2.45 GHz bandwidth, a phase fluctuation of areception wave occurs by depending on a communication distance betweenthe wireless identification IC tag and the reader for wirelessidentification IC tag, and a phase-shift function to compensate for thisfluctuation has been given, thereby increasing the circuit scale.According to the configuration described in FIG. 1, it is possible tosimply configure the receiving circuit.

FIG. 2A-2D are diagrams illustrating waveforms of the reader forwireless identification IC tag of the present invention. A waveform Ashows a signal of the control signal line 112 of FIG. 1. A waveform Bshows a signal of the transmission line 103 of FIG. 1. A waveform Cshows a signal of the reception line 106 of FIG. 1. A waveform D shows asignal of the reception signal line 113 of FIG. 1. By a signal A, thesignal of the high-frequency generator 101 is controlled by the NORcircuit 102, and a waveform like the signal B is outputted. At the sametime, by the signal A, the MOS transistor 111 is turned off after beingturned on, so that charges of the second capacitor 110 is discharged.

A signal C is a signal from the wireless identification IC tag, and isdivided into a signal having large amplitude and a signal having smallamplitude. The one having large amplitude indicates a logic “1”, and theone having small amplitude indicates a logic “0”. A signal D is a valueoutputted by integrating the signal C. This integration is performed insuch a manner that charges stored by the first capacitor 107 and thefirst diode 108 are rectified by the second diode 109, therebyaccumulating the charges on the second capacitor 110. If the time toreach a voltage V1 shown in FIG. 2D is measured by the control circuit601, “1” or “0” can be discriminated. That is, as shown in FIG. 2,assuming that the time to reach V1 is taken as T1 or T2, if T1 issmaller than T2, it is shown as “1” in the case of T1, and it is shownas “0” in the case of T2. Since T1 and T2 may be relatively comparedwith each other, an accuracy of the measurement can be increased. By thecomparison, it is possible to discriminate whether the data from thewireless identification IC tag chip 606 of FIG. 6 is “0” or “1” and makeout an ID number of the wireless identification IC tag chip 606 of FIG.6 by the transmitting and receiving circuit 602 and the control circuit601 of FIG. 6.

As described above, when the detection is performed by using therectification and integral circuits, the reader for wirelessidentification IC tag and the wireless identification IC tag systemexcellent in economical efficiency in terms of the circuit scale or theelectric power consumption can be realized. Further, since activeelements are not contained inside these detection circuits, a stableoperation can be realized. Still further, since integration is utilized,weak signals can be handled. Note that, such a detection circuit cantake the same structure even in the receiving circuit of the wirelessidentification IC chip 606 shown in FIG. 6.

Second Embodiment

A reader for wireless identification IC tag described in this embodimentuses the same circuit configuration as that of FIG. 1 and uses a crestvalue of the reception waveform of D in FIG. 1 as a means ofdiscrimination.

FIG. 3A-3D are other diagrams illustrating waveforms of the reader forwireless identification IC tag of the present invention. A waveform Ashows a signal of the control signal line 112 of FIG. 1. A waveform Bshows a signal of the transmission line 103 of FIG. 1. A waveform Cshows a signal of the reception line 106 of FIG. 1. A waveform D shows asignal of the reception signal line 113 of FIG. 1. By the signal A, thesignal of the high-frequency generator 101 is controlled by the NORcircuit 102, and a waveform like the signal A is outputted. At the sametime, the MOS transistor 111 is turned off by the signal A after beingturned on, so that the charges of the second capacitor 110 isdischarged. the signal C is a signal from the wireless identification ICtag, and is divided into a signal having large amplitude and a signalhaving small amplitude. The signal having large amplitude indicates alogic “1”, and the signal having small amplitude indicates a logic “0”.The signal D is a value outputted by integrating the signal C.

As shown in FIG. 3, the sample time of the signal D is fixed as T3, andwhen assuming that the voltage at this point is taken as V2 or V3, if V2is larger than V3, it is indicated as “1” in the case of V2, and it isindicated as “0” in the case of V3. Since V2 and V3 may be relativelycompared with each other, it becomes possible to increase accuracy. Thetwo voltages can increase a reading resolution by being compared with ahigh degree of accuracy by using a differential amplifier circuit andthe like inside the control circuit 601.

Third Embodiment

FIG. 4 is another diagram illustrating a circuit of a reader forwireless identification IC tag of the present invention. An output fromthe NOR circuit 102 is returned to the input by a feedback line 401, andhas a self-oscillating function. A control signal line 112 is alsoconnected with this NOR circuit. An output from a NOR circuit 102 isinputted to a circulator 104 as a transmission line 103. The circulator104 is connected with an antenna 105, and a reflected wave receptionsignal from the antenna 105 is outputted to a reception line 106. Thereception signal of the reception line 106 is inputted to a firstcapacitor 107. This first capacitor 107 plays a role of fixing anamplitude voltage of the reception signal. An output of this firstcapacitor 107 is inputted to a first diode 108 and a second diode 109.This first diode 108 plays a role of fixing the lowest level of thereception signal. The second diode 109 has a role of transmitting theenergy to one direction. An output of the second diode 109 is connectedto a second capacitor 110. The second capacitor 110 has a role ofaccumulating the energy from the second diode 109. A function ofdischarging the energy of the second capacitor at right timing isrealized by a MOS transistor 111.

This circuit of FIG. 4 does not require a special high-frequencyoscillator. Hence, it becomes possible to reduce the circuit scale. Asignal of the control signal line 112 makes the performance of thecontrol to the second capacitor common through control of ahigh-frequency oscillator and the MOS transistor 111, thereby making thecircuit simple. Waveform as the result of this simplification is thesame as the waveforms illustrated in FIGS. 2A-2D and 3A-3D.

Fourth Embodiment

FIG. 5 is another diagram showing a circuit of a reader for wirelessidentification IC tag of the present invention. By a high frequencygenerating circuit 501 by Bluetooth, a high frequency is generated andinputted to a NOR circuit 102. A control signal line 112 is alsoconnected with this NOR circuit. An output from a NOR circuit 102 isinputted to a circulator 104 as a transmission line 103. The circulator104 is connected with an antenna 105, and a reflected wave receptionsignal from the antenna 105 is outputted to a reception line 106. Thereception signal of the reception line 106 is inputted to a firstcapacitor 107. This first capacitor 107 plays a role of fixing anamplitude voltage of the reception signal. An output of this firstcapacitor 107 is inputted to a first diode 108 and a second diode 109.This first diode 108 plays a role of fixing the lowest level of thereception signal. The second diode 109 has a role of transmitting theenergy to one direction. An output of the second diode 109 is connectedto a second capacitor 110. The second capacitor 110 has a role ofaccumulating the energy from the second diode 109. A function ofdischarging the energy of the second capacitor at right timing isrealized by a MOS transistor 111.

Bluetooth is a near-field communication system operating at 2.45 GHz. Itis often the case that this system is practiced in use in a mobileterminal also. Hence, practical use of this oscillating function ofBluetooth is effective as bringing about simplification to make thecircuit common. Waveforms are the same as those of FIGS. 2A-2D and3A-3D. Further, even if Bluetooth is employed, other circuitconfigurations remain unchanged from the first embodiment. While thereare various circuits for the high-frequency oscillator, there is afeature of allowing a shared use with original Bluetooth functions byemploying Bluetooth.

In the foregoing, the invention made by the inventor of the presentinvention has been concretely described based on the embodiments.However, it is needless to say that the present invention is not limitedto the foregoing embodiments and various modifications and alterationscan be made within the scope of the present invention.

INDUSTRIAL APPLICABILITY

The reader for wireless identification IC tag of the present inventionis a technique advantageously applied to mobile equipments requiringdown-sizing, particularly, such as mobile phones and PDA (PersonalDigital Assistant), and it is not limited to these, but is widelyapplicable to various wireless communication equipments.

1. A reader for wireless identification IC tag receiving a reflectedelectromagnetic wave from a wireless identification IC tag, the readerfor wireless identification IC tag comprising: a receiving circuitintegrating the reflected electromagnetic wave; and a first circuitdiscriminating an intensity of the reflected electromagnetic wave basedon a signal integrated by the receiving circuit.
 2. The reader forwireless identification IC tag according to claim 1, wherein the firstcircuit discriminates the intensity of the reflected electromagneticwave by a comparison of relative intensities before and after.
 3. Thereader for wireless identification IC tag according to claim 1, whereinthe reader for wireless identification IC tag comprises a first signalto serve as a trigger at the time of transmitting a transmissionelectromagnetic wave toward the wireless identification IC tag, and anintegral value at the receiving circuit is reset with synchronizing withthe first signal.
 4. The reader for wireless identification IC tagaccording to claim 1, wherein the reader for wireless identification ICtag has a Bluetooth circuit for performing Bluetooth communications, andgenerates a transmission electromagnetic wave to be transmitted towardthe wireless identification IC tag by using an oscillating function ofthe Bluetooth circuit together.
 5. The reader for wirelessidentification IC tag according to claim 1, wherein the reader forwireless identification IC tag is provided in a mobile phone.
 6. Areader for wireless identification IC tag comprising: a high-frequencygenerator generating a transmission electromagnetic wave; a secondcircuit outputting the transmission electromagnetic wave generated bythe high-frequency generator with synchronizing with a first signal; anantenna transmitting the transmission electromagnetic wave outputted bythe second circuit toward the wireless identification IC tag, andreceiving a reflected electromagnetic wave from the wirelessidentification IC tag; a diode rectifying the reflected electromagneticwave received by the antenna; a capacitor storing an integral value of asignal rectified by the diode; and a switch discharging the capacitorwith synchronizing with the first signal, wherein the integral valuestored by the capacitor is discriminated, thereby obtaining informationfrom the wireless identification IC tag.
 7. The reader for wirelessidentification IC tag according to claim 6, wherein the second circuitis a NOR circuit to which an output of the high-frequency generator andthe first signal are inputted.
 8. The reader for wireless identificationIC tag according to claim 6, wherein the high-frequency generator andthe second circuit are realized by a NOR circuit to which a feedbacksignal of an output and the first signal are inputted.
 9. A wirelessidentification IC tag system comprising a wireless identification IC tagand a reader for wireless identification IC tag, the reader for wirelessidentification IC tag transmitting a transmission electromagnetic wavetoward the wireless identification IC tag, and the reader for wirelessidentification IC tag receiving a reflected electromagnetic wave fromthe wireless identification IC tag, wherein the reader for wirelessidentification IC tag includes: a receiving circuit integrating thereflected electromagnetic wave; and a first circuit discriminating anintensity of the reflected electromagnetic wave based on a signalintegrated by the receiving circuit.
 10. The wireless identification ICtag system according to claim 9, wherein the first circuit discriminatesthe intensity of the reflected electromagnetic wave by a comparison ofrelative intensities before and after.
 11. The wireless identificationIC tag system according to claim 9, wherein the reader for wirelessidentification IC tag has a first signal to serve as a trigger at thetime of transmitting an electromagnetic wave toward the wirelessidentification IC tag, and an integral value at the receiving circuit isreset with synchronizing with the first signal.